This invention relates to an electrical machine, more particularly a motor or a generator, with a winding comprising a winding wire consisting of individually insulated conductors, these conductors being wires or strands.
This kind of wire is commonly known as Litz winding wire.
Such windings are for instance placed around the teeth of the stator or in grooves in the stator, which teeth or grooves extend parallel to the rotation axis of the rotor.
In known motors or generators, the conductors of the winding wire of the winding extend parallel to each other or are twisted in small bundles, which extend parallel to each other. These small bundles may for instance consist of Litz wires having twisted or braided wires, the winding wire comprising several of such Litz wires which extend parallel to each other.
The heat conduction of the winding perpendicular to the direction of the winding is very small compared to the heat-conduction of copper. Therefore the winding is often impregnated with special materials to increase the thermal conductivity, but even then the thermal conductivity in transversal direction of the winding is relatively small and the possible cooling of the winding is limited.
EP-A-0.519.679 discloses a tubular three-phase armature winding, the wire used for the winding comprising parallel flat conductors. The winding wire extends in zigzag between the both ends of the motor, but in a traverse section of the winding wire, the conductors are adjacent to each other in the traverse direction and these conductors extend parallel to each other in the longitudinal direction of the winding wire. This document define a very space efficient winding arrangement but does not mention any cooling and the winding has the same limited cooling possibility as the above mentioned known motors and generators.
The lack of sufficient cooling of the winding may constitute a limit to the speed of the motor or generator.
The invention seeks to provide an electrical machine with a winding having an increased cooling.
In accordance with the invention, this object is accomplished in that the conductors of the winding wire extend inside the wire in a zigzag pattern under angles with respect to the mean longitudinal direction of the winding wire, between the edges of the winding wire, said edges being in thermal conductive contact with a cooling medium.
In a section perpendicular to the winding, and in the transversal direction there is only one winding wire with in zigzag extending insulation conductors.
By the zigzag pattern, the heat can be transferred along the conductors to the edge of the winding and so to the cooling medium instead of having to jump through the insulation from one conductor to the other and the heat may be dissipated laterally to a much greater extent than when the conductors are parallel.
DE-C-496.884 discloses a method for manufacturing a winding wire wherein the conductors extend from on edge of the wire to the other. However this document does not disclose how such wire is used in a winding. Nothing is suggested that the edges of the wire are also the edges of the winding and are in thermal conductive contact with a cooling medium. On the contrary, with the purpose of cooling, the winding wire may be hollow, comprising thus a channel for cooling air.
According to the invention, the zigzag pattern may be under angles between 5xc2x0 and 45xc2x0 and preferably between 10xc2x0 and 30xc2x0 with respect to the mean longitudinal direction of the winding.
More particularly, the winding wire may consist of a wire formed by a flat and wide packet of insulated conductors, each conductor extending in zigzag from one side of the packet to the other.
The winding may be in heat conductive connection with a solid heat conducting material, for instance the iron of a stator, in which case the cooling medium consists of this heat conducting material.
The winding may be situated in a channel in a stator, whereby in a form of embodiment, space is left open in the channel, which space is filled with a liquid or gaseous cooling medium, for instance transformer oil.
The winding wire may be impregnated with a suitable varnish so that the winding becomes self-supporting. In this case, the winding may be used in an air-wound motor and the cooling medium may be gaseous.